Rolling mill with closed frames and with a control system for continuously and rapidly adjusting the roll gap



Nov. 15, 1966 K J. NEUMANN 3,285,049

ROLLING MILL WITH CLOSED FRAMES AND WITH A CONTROL SYSTEM FOR CONTINUOUSLY AND RAPIDLY ADJUSTING THE ROLL GAP Filed Feb. 13, 1963 2 Sheets-Sheet 1 Nov. '15, 1966 K. J. NEUMANN 3,285,049 ROLLING MILL WITH CLOSED FRAMES AND WITH A CONTROL SYSTEM FOR CONTINUOUSLY AND RAPIDLY ADJUSTING THE ROLL GAP Filed Feb. 15, 1963 2 Sheets-Sheet 2 6 b Fig.2

4 Claims. ci. 72-246) This invention relates to a rolling mill with closed frames and with a control system for continuously and rapidly adjusting the roll gap in order to obtain a rolled material with close tolerances, and more particularly to a rolling mill in which the frames, prior to a rolling operation, are put under a certain pre-stress by hydraulic pressure, which pre-stress is kept constant during the rolling operation by the control system, in that the hydraulic stressing force is changed as a function of the actual rolling pressure or of the elongation of the frames. The constant stress in the framesnot taking into account certain other influences as for example roll-bendingmeans a constant roll gap and therefore rolling stock with close tolerances.

By the French patent specification No. 1,069,471, a controlled rolling mill with solid, normally stiff frames has been known, which are, prior to rolling operation, hydraulically pre-stretched to half the maximum admissible amount. Variations in frame-stretch due to the changing roll pressure are determined by stretch gauges and fed into the control system which, at rising rolling pressure or increasing frame-stretch, respectively, diminishes the hydraulical stressing force used for the pre-stretching of the frames to such an extent that the frames return to their original lengths.

It is an object of this invention to better adapt the aforementioned control system to a rolling mill with closed frames, as it has been recognized that, in solid, closed frames, the control system had to be extremely sensitive on account of the relatively small values measured for stretch variations in such frames.

It is therefore a further object of this invention to incorporate a metallic and elastic member into the flowpath of both the rolling pressure, and the hydraulic pressure used for pre-stretching of the frames of a controlled rolling mill. This elastic member thus represents together with each frame a system of springs arranged in series so that the total spring coefficient (in mm./ ton) of the pressure receiving parts will be larger than that of the frame taken alone, in order to increase the deviations from the desired roll gap value and the value to be controlled, thus reducing the demands on the sensitivity of the control system.

Heretofore the tendency was to build rolling mill frames as stiff as possible in order to achieve close tolerances of the rolled stock, independently of the fact whether the rolling mill was controlled or not. By this invention it is being taught that a rolling mill should be softened, when a control system is to control, i.e., to keep constant a given frame-stretch. The softening of a rolling mill by the insertion of elastic members into the flow-path of the rolling pressure makes it possible to obtain best regulating effects even with stiff stands. Furthermore the rolling mill may be used, in case of difliculty with the control system, as an unregulated mill with normal stiffness by simply bridging or replacing the elastic members by stiff spacers. On the other hand, existing rolling mills with closed frames may be turned into a regulated mill through the use of elastic members.

The elastic members are made of metal, especially of high-grade steel, in order to obtain a Spring-characteristic as linear as possible. Purely hydraulic pressure-cushions United States Patent 3,285,649 Patented Nov. 15, 1966 ice are not to be considered as elastic members in the scope of this invention, as the compressibility of a liquid preS- sure medium, i.e., its elasticity, depends on the pressure, the temperature and the height of the liquid-column.

Further objects and advantages of the rolling mill of this invention will become apparent from the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 shows a 4-high rolling mill with a schematicallydrawn control system based on the measurement of the rolling pressure;

FIG. 2 shows the bottom part of the same mill with an elastic member of special design, and means for measuring the elongation; and

FIG. 3 shows the measuring means of FIGURE 2 in an enlarged scale.

With continued reference to the drawings, there is shown in FIGURE 1 a rolling mill, including upper chock 1 and screw-down spindles 2, between which an elastic member 3 in the shape of a membrane is inserted in each frame. Each elastic member 3 is pre-stressed prior to a rolling operation by a pair of spreading pistons 4 acting between the upper chock 1 and the lower chock 20. The hydraulic stressing force passes across a pressure gauge 5 and the upper and lower traverses 6a and 6b respectively into the frame-columns 6, thereby stressing these columns too.

The shown installation of the spreading pistons 4 is known per se for the purpose of weight-balancing of the upper chocks with the upper roll. In the scope of this invention such a spreading device has to be dimensioned for the pre-stressing of the spring-system consisting of frame columns 6 and the elastic member 3. The prestressing force should be at least 20% the maximum rolling pressure per frame.

The spreading pistons 4 are supplied with a high hydraulic pressure by a pressure-multiplier 8 by way of conduits 7. At the low-pressure side the pressure multiplier 8 is connected over conduit 9 to a control valve 10. Conduct 11 leads to a pressure source (not shown); conduit 12 is for back feeding. The piston-rod 13 of the control valve 10 is positioned by an adjusting member in the control system 14 which member is preferably operated electromagnetically.

The measured value from the pressure gauge 5 which amounts to the sum of rolling pressure-l-hydraulic stressing force created by the spreading piston 4, is introduced into the control system 14 by way of conduit 15. This sum of force is compared in the control system 14 to a preset value and kept constant, in that deviations from the desired preset value cause a displacement of the piston rod 13 of the control valve 10, thereby causing a pressure variation in conduits 7 leading to the spreading pistons 4. In case of an increase of the rolling pressure and hence of the sum value of forces measured by pressure gauge 5, the piston rod 13 is displaced to the right hand side so that conduit 9 is opened to back-feeding conduit 12, thus allowing a diminution of the hydraulic stressing force sufficient to maintain the sum of the forces equal to the desired preset value in spite of the additional deformations of elastic member 3 and the increased elongation bf the frame columns 6, as resulting from the increased rolling pressure. A constant load on the presure gauge 5 means a constant load both on the elastic member 3 and on the frame columns 6 and hence constant lengths of these spring elements, which is equivalent to a constant roll gap.

The principle of the described control system maintaining the sum of rolling pressure-l-hydraulic stressing force constant in all parts of a stand submitted to the rolling pressure is described in the prior US. Patent No. 3,124,-

982, in connection with rolling mill stands including tierods and for separate detection of the rolling pressure and the hydraulic stressing force, whereby the summing up is effected in a separate adding apparatus.

As shown in FIGURE 2 an elastic member of special design is installed between the lower chock 20 and the bottom traverse 6b of the frame. It consists of several telescopically arranged cylinders 21 to 25, of which the outer cylinder 25 rests on a centering plate 26 located on traverse 6b, and the inner cylinder 21 is reacting against the lower chock 20. The other cylinders 22 to 24 are arranged in series in the force flow-path with the outer and inner cylinders 21 and 25. This is achieved by means of inner and outer collars provided on the cylinders 22 and 24. The force flow passes these collars and enters the adjoining cylinders 21, 23 and 25 which are not provided with such collars. In an elastic member of this design all cylinders are stressed either only by a tension or only by a pressure, so that an essential linear spring-characteristic is obtained.

The elastic member according to FIGURE 2 is in addition provided with a measuring device for detecting the axial length of the elastic member. For this purpose the inner cylinder 21 has a closed bottom 21a at its free end, on which parts of the measuring device, shown in FIG. 3 at an enlarged scale, are fastened. The measuring device includes a measuring rod 30, axially adjustable relative to a lower socket 31, and a differential transformer 32 fastened to the bottom 21a of the inner cylinder 21 by means of a support 33. The lower socket 31 rests on the centering plate 26 thus being solidly fixed. The measuring rod 30 enters the dilferential transformer 32 with its free end; the differential transformer follows the displacements of the bottom 21a of the inner cylinder 21 as resulting from variations in rolling pressure and moves relatively to the measuring rod 30, thus giving corresponding measured values. These measured values replace as elongation values the sum of rolling press-ure-l-hydraulic stressing force in the pressure gauge of FIGURE 1, and are introduced in the same way via conduit into the control sysetm 14 for comparison with a preset desired value.

In this case too, the roll gap remains constant as long as the axial length of the elastic member measured between its back-up points is kept constant by the regulating system; as for a. given axial length the force passing through the elastic member is always the same and therefore the length of the frame-columns 6 or the stress in these columns also remains constant.

The adjusting device of the measuring rod 30 with a setting nut 34 and a blocking nut 35 serves the purpose of adjusting the measuring rod 30 relative to the differential transformer 32.

An elastic member according to FIGURE 2 has the further advantage that the number of cylinders may rapidly be changed in order to modify its spring-coefiicient. Depending on the deviations to be expected due to irregularities of the rolled stock, a larger or smaller springcoefiicient is desired for precise detection of the measured values of elongation. In cold rolling mills the spring coefiicient of an elastic member is suitably established between .001 to .005 mm. per ton.

I claim:

1. In a rolling mill comprising two solid, stiff frames consisting of an upper and a lower traverse connected by upright columns, a pair of checks mounted in the frames and rolls rotatably mounted in the chocks and spaced from each other to form a suitable roll gap, in combination an elastic metallic member disposed in each frame between at least one chock and a traverse of the frame, means for hydraulically pre-stressing the frames and said elastic members to a predetermined stressing force prior to a rolling operation, .a measuring devicefor detecting and signalling the actual axial length of at least one of said members, and a control system for adjusting said hydraulic stressing force in each frame in response to the signals of said measuring device to keep the axial length of said members constant.

2. A rolling mill according to claim 1 including hydraulically operated spreading devices acting between the upper and lower c-hocks of each frame for pre-stressing said frames and said elastic members.

3. A rolling mill according to claim 1 in which the inner cylinder of each of said elastic members has a closed end facing the adjacent chock and the outer cylinder is resting at its outer end on the inner surface of the adjacent traverse, said measuring device being disposed between said closed end and said inner surface for the outer cylinder for detecting the axial length of said member.

4. An elastic member according to claim 3 in which said measuring device consists of a measuring rod and a differential transformer, said measuring rod being mountd on said inner surface for the outer end of said outer cylinder and said differential transformer being fastened to said closed end of said inner cylinder, said measuring rod extending into said transformer for transmitting elongation changes in said columns.

References Cited by the Examiner UNITED STATES PATENTS 2,027,283 1/1936 McFadden -563 2,430,410 11/1947 Pauls 80-56.3 2,900,818 8/1959 Starr 73-88.5 X 3,075,417 1/196-3 Blain 80'56 .3 3,804,542 4/ 1963 Statha-m 73-441 3,111,047 11/1963 Metzger 8056.3 3,159,063 12/1964 FOX 7221 FOREIGN PATENTS 1,069,471 2/1954 France.

644,957 5/ 1937 Germany.

CHARLES W. LANHAM, Primary Examiner. C. H. HITTSON, Assistant Examiner, 

1. IN A ROLLING MILL COMPRISING TWO SOLID, STIFF FRAMES CONSISTING OF AN UPPER AND A LOWER TRAVERSE CONNECTED BY UPRIGHT COLUMNS, A PAIR OF CHOCKS MOUNTED IN THE FRAMES AND ROLLS ROTATABLY MOUNTED IN THE CHOCKS AND SPACED FROM EACH OTHER TO FORM A SUITABLE ROLL GAP, IN COMBINATION AN ELASTIC METALLIC MEMBER DISPOSED IN EACH FRAME BETWEEN AT LEAST ONE CHOCK AND A TRAVERSE OF THE FRAME, MEANS FOR HYDRAULICALLY PRE-STRESSING THE FRAMES AND SAID ELASTIC MEMBERS TO A PRE-DETERMINED STRESSING FORCE PRIOR TO A ROLLING OPERATION, A MEASURING DEVICE FOR DETECTING AND SIGNALLING THE ACTUAL AXIAL LENGTH OF AT LEAST ONE OF SAID MEMBERS, AND A CONTROL SYSTEM FOR ADJUSTING SAID HYDRAULIC STRESSING FORCE IN EACH FRAME IN RESPONSE TO THE SIGNALS OF SAID MEASURING DEVICE TO KEEP THE AXIAL LENGTH OF SAID MEMBERS CONSTANT. 